Compression rheostat



Feb. 7, 1928. 1,658,787

A. M. LEVY COMPRESSION RHEOSTAT Original Filed June 4, 1919 Q J3 l '1 l 2f 36 36 fizz-Eli J.)

ill;

,4 TTOR/VE Y Patented Feb. 7, 1928.

UN TED- STATES AARON MICAH LEVY OF NEW YORK, N. Y.

1,658,782? PATENT OFFICE.

, ASSIGNOR OF ONE-HALF TO MAURICE SAM- BURG, OF NEW YORK, N. Y., AND JULIUS C. HOCHMAN, OF PASSAIC, NEW JERSEY.

COMPRESSION RHEOS'IAT.

Application filed June 4, 1919, Serial No. 301,710. Renewed November 12, 1925.

This invention is an electric controller which effects an entire and uniform control of electric currents. It can form an instrument by itself or it: can form part of another instrument or devicc. It can entirely nterrupt orit can regulate electric currents and can do it very rapidly or slowly.

The change in electric conductivity is brought about byl diflerences in contact of electric conducting bodies, according; to the well known effect. In my instrument this principle of difference df contact is accentuated andcontrolled bysuitable' means, to be here described as the principal means'of hringing about' this great variation of contact of electricconducting 'bodie s." The special electric resistance material consists of :an intimate and uniform mixturof electric amt-electric non-conducting 'inattef iii-a fine natureso= as to impart compressible and resilient nature to the-entire"composition? \Vlien this mate-ii al j s "under no or slight compression, it's 'constit'uent are'in' ve ry' light contact and its electric conducting particles touchfveryilight ly notyat all. The 'conducting'an' being all interspersedthere be but' very; minute ifany conducting paths' andfjth'e ma terial-in' that condition ispractically an in sulatorl' Y I i-is-iu'creasmg pressure is applied the volume'of the-material grows smallr, the par ticles P come *more and "more into contact; paths of i conductivity form and grow larger; as more conducting particle's into con tact andinto more intimate contact';-"and the eectric conductivity therefor?lincreases. hen the material is firmly compressed the conducting particles are in "close contact.- enough of these particles are in c'lose'c'on'tact toform a path of good conductivity,andthe material inthis condition is a fa rly good" conductor, the resistance may be only a small fraction of an ohm. f

The material need not be made of any particular substances butmust have a general nature and identification of'compressihility, resiliency and uniformity of constitution. It must have the same proportion and the same density of material throughoutits mass. It should have the same propor- ..tion 'ot n'mterial, the conducting and non- "conductii'igniatter interspersing,-"so that there should be no undue amount of conductin matter by itself to form a path of good or fair conductivity. Such paths would per niit a flow of electricity at all times even under light or no pressure, and with currents of considerable amounts there would be rapid heating of these paths ano a rapid increase of conductivity. It would soon resultprobably in the destruction of the material by a ycry high temperature and there certainly could be no control of current by means of s uch a material. There must also beia 'gencr'al regularity, at least, of density of material. There mustbe no packing of material as. this would result in an area of good conductivity with the same deleterious effects' in a lesser degree. Slight irregular- Tty of density is. not harmful.

To'obtaiu a naterial' of the above nature 5, f fiat-erial should be made of suitable substate, part of which inus'tbeof a resilient;

'stancesand by suitable means. With substances of anon-adhesive nature such a ma- 5. terial can; bereadily made. Mere thorough mechanical mixtures Willbe sufficient. Mica in jthefformof'fiakesor slivers and carbon or graphiteinaifineforin makes a very elficieut mixture- "nape-amou prefer a mixture ofitli'e' finizrmica flakes and graphite-flakes. 'Wh e n however the non-conducting matter is of adhesive natureas the longer fibres of *abtfbs particularly are, a special process must-be employed whichis also specially applicable to the shorter fibres, as follows:

: tatioir off the liquid. Because of the adlie 9 sivenesso'f'the fibrous matter and the nonadhesiveness of the conducting particles, and the loose condition in which the fibrous matter is from; which condition is accentuated by the treatment, the tendency is for the con- Tlie' filjrous materi alpreferably'in a loose c Jlldllllol'ij i s 1mn1 ersed,for'a suitable time,

in a. liquidfpreferably water, in which elec ducting particles to enter into contact with and form a coating over each and every fibre. the coating being a uniform film, and the particles touching lightly, when they touch at all. The material is then separated from the liquid and dried, when it Will form a n'iaterial consisting of an intimate and uniform combination of fibre and conducting particles.

On separating the "material from the liquid, when t is in a very pliable condition, it should be castinto th'e' frin ofa thin layer and then dried. It then forms a soft felt 0r mat like material of practically uniform density. adhering together in the form in whiclr itwas cast,v and is-1a speciatlyetficient and suitable resistance material. This liquid treated combined resistanee ri'ifitiiiifi could also be used in the form of cloth. The short fibrousmaterial,that'isthe mixture or combination of short fibers and conducting particles,' can be given a felt or mat like form by coating it' on metal supports, which can be effected 'bymealns of cement, or by merely drying the material on the metal supports.

A suitable'p'ortion of this. material in any of its different forms or aco'inbin'a'tion of its'di'ilerent or some'of'its different forms, together with'suitable aces 0rifes, inakes an cfi'icien't regulator for sniatltuirents' andl'for curr'ents' I of lotv' volta'ge'. VVith currents .of high 11y lta e nd' considerable am erage, as f currents 10f the rcingv'al'ue very' coinplic' atiii gfihd litant phenomena aii diet-v fectS would appear: Ori'closi'n'gthe ,electric circuit the curre'nt would 'rise. frapidly and would destroy: the, mater al I a high temperature' unlessthe current was interrupted,

as by blowing a 'fiise etc 4 This rise in conductivity 'seemsto be due to particleslof conducting. inatter 'f coheririgfftliat 5 is joining firmly,'m'a'l ti ng good contacts, aiicltherefore areas ofgood condl k fiivit rehearing efictsiandghtgh y' spread, With't :resultj as stated above. T liese etlet sl'however, taxis; place. highervoltage ti ve '20 'mfgeawheajthe is. largeririflplro ortionatithe same re ers fifty; dgidiitgj g; resist- 1t i"se ti e aa i ie i heat r dii d" not *ercf ate-"p ope h e ation tolthef ainp ijage these etfe'c ts' will be, obviated; 1 3

The lower the current fiow in amperes the higher the voltagejcahfbf the: cur: rent is only abfo'ut it-half la IIipre, the v woltage. can b'e'over" ohe'diundredf Witlt lowvo ta ges" the amperage may; be eryQIJarge, it is possible also to'arr ang'e the sections" in parallel; so aswaive amperage garrd high voltage, thatqisitol. split the 'amperage and not the voltage. 4 1: Thesesectionsconsi st of a portionof resista iifce material between containingwalls, as a resistance -mate'rial separatedby ;intersecting mus; or? portionsv of material may be placed in separate. .icontainers, electrically connected. Prwisionshouldbe made for permitting the escape of heat, and also for permitting slight .eggpansion. in. the'containing wall away from the K131361131. to maintain a uniformitybf pressure as -thematerial also expands slightly with heat.- .-Th1S however is not marked and is not important with the non-fibrous, resistance materials,

p1,! I 1 A gemperature rapidese areas of The drawings show a very convenient form ot'intersectin'g or containing-Wall. A piece of metal is bent over into a form 01 double plate with an air space between as shown. It thus has ample.-lventilation= and radiating surfaces; andfcan'cxpand away from the contained resistance material. The rsi'slfiri e e eliiment consists of metal plates and thin mats of resistance material placed alternately. The plates and mats of resistance material are movable, so that pressure applied to one section is transmitted to all. The variation of conductivity tal esplace not only by means of the differences of contact of the conducting particlesof the resistance material, butalso by the variation of contact between. the conductingparticles of the resistance material and the metal plates. ,The variation in pressure is here obtained 'bymeans of aregula'ting screw, but may be, obtained by other ineans.

This'j'rheostat is very efficient, even ordi nary mixturesotfibre and fine conductinginatt cr inot l iquid. treated, but; used in the loose felt condition between these plates will make a fairly,goodarheostat for-soniepurposes. The liquid treated material--is how ever the only really etticient'fibrous material and should be used, 'as in conjunction with the-intersecting splates, it gives a uniformand entirerange of resistance and for the. larger apparatus the material to' be preferred-overall others. v

For small amounts of; current aswhen usedin a; socket form for dimmingcincam (lescent rglights' the' mixture ;containing ithe non-fibrous. matter is preferable as sit is easiest handled-j In particular I use the mixtures containing miea. The drawings show a combinationof-rheostatanai lamp" socket. The-variation -in' cont-att here takes place between the conducting particles of the mixture and; the regulating screw which is also one ofijthe electric contact parts. This screw also acts as part bfthecontai-nen con fining the -material and preventing=any loss of it from the receptacle; This deviee contains -means.-f0r breaking the electric con-' tact at a point of light pressure,- andlfor short 'circuit-ing the resistance element ata period of firm? pressure.

This appliance has whatis known as an Edison socket-for receiving the electric'lam'p' or other such device,- ai1'd a screw plug" for fitting. into an, Edison socket: N 0' special means for heat radiation,-0r:ventilation"is provided in. this instrument,- although such means could be easily 'installedand would be found helpful fol-larger currents? than are ordin'arilyiused in incandescent lamps. For lamps suchas are ordinarily usedin residences and such devices, the socket rheostat as substantially shown is sufiicient v t willbe seen by thesetdescriptions, that the variation in;conductivity, is brought secting parts or container parts and the conducting particles, there may be also relatively large conducting bodies intersecting the resistance -material, and assisting the variation in conductivity. These relatively large conducting bodies increase the power of higher resistivity in the circuit by reason of their relatively smooth surface, and the lack of tendency of the conducting particles to cohere or come in close contact therewith. Under light pressure the conducting particles are in lighter contact with these larger conducting bodies, which are usually oralways metal, than they are with each other, hence the higher resistivity. This applies particularly to the fibrous materialsin wchich the conducting particles are in closer contact than the conducting particles .in the nonfibrous mixtures. 1

By reason of the efficacious actionand assistance given by the contact, anddntersecting parts and the use of separate containers, considerable efiiciency canbe obtained by the use of these means in conjunction with other resistance material than that invented by me. Metal plates of the general type as. that shown in the drawing would be very efficient in maintaining the-same conditions; of temperature and pressure and breaking up cohering 'efl'ects. Electric contact parts,; ha-ving a spring effect or of special shape would also be effective inconnection withrelatively large bodies with. electrically sensitive con-- tact. surfaces,- that is bodies which vary;.their electric resistance through .variation-;of contact, as bodiesof carbon or;g'raphite or containing carbon. orgraphite-and a; non-conducting matter. Such contaet.. parts asde-- scribed would be inserted --.between such poorly conducting parts: or bodies as,- those of the sovcalled graphite of commerce.

This case is relatedto'mycompanion case,

Serial No. 411,778, filed J une. 4, 1919. issued concurrently herewith and the :claims generic to the two applications are presented in the companion case. i

The followingis what I consider a good means of carrying out this invention and the following drawings should. be referred. to for a complete understanding of the specification which follows In the drawings Fig. 1 is a side view in elevation of the preferred form of this inventionillustrating the device constructed for use in ordinary electric lamp sockets.

Fig. 2 is a vertical sectional view through Fig.1.

-Fig. 3 is a vertical sectional view through the device taken at right angles to Fig. 2.

Fig. 4 is a horizontal sectional View through the center of the device illustrating the compressor, screw, and other parts relating thereto, removed.

Fig. 5 is a view partly in section, of a modified form of controlling knob of the device.

Fig. 6 is a fragmentary view similar to Fig. 2, illustrating the use of a fibrous resistance element and Fig. 7 is a horizontal sectional view through a modified form of rheostat illustrating the same adapted for use for heavier currents.

Similar reference numerals indicate like parts in all of the figures where they appear.

, cferring to the drawings in detail the numeral 1, designates the main body of the device which is preferably formed of porcelain or a similar insulating material. This body may be cylindrical as illustrated in Figure 4 and provided at one end with a reduced extension or plug 2. Extending longitudinally through the plug 2 is a bore 3 the inner end of which communicates with a transverse passage 4: formed in the plug and body which passage opens out through the side thereof. The transversely extending centrally exposed passage 5 is formed in the body 1 and extends at right angles to the passage 4 previously described. From a point about midway of the length of the passage 5 there is provided an enlarged bore 5 ;and a groove 6 as clearly illustrated in Figure 2. Extending longitudinally through the body 1 from the under side thereon and off setfrom the longitudinal axis is an aperture-7, the inner end of which communicates with.. the groove 6. Parallel with the opening 5 is a transverse bore 8 arranged slightly beneath said opening and this bore 8 extends from the inner wall of the groove 6 through theinner wall of a recess 9,-formed in the body immediately beneath the rear terminal ofthe passage 5. A, recess 10 is formed in the, under side of the body and is slightly off sctfrom the center thereof.

Surrounding the plug 2 is a threaded shell 11 having formed on the inner end thereof, a tongue '12 to which is-connected a contact strip 13. This strip extends across the rear end of the passage 5 and is provided with an inwardly off set portion 14 which seats in the recess 9 herein before described. Extending through the ofi set portion leis a screw 15, the inner end of which is threaded into a contact plate 16 arranged against the inner wall of the groove 6. It will be understood that this contact plate is surrounded by a suitable insulating material 17 as will be clearly seen upon reference to Figures 2 and 4. Seated in the enlarged bore 5 is an internally screw threaded bushing 18 which is notched at its extreme inner end to receive the insulation 17 and'this bushing is held in place by zfi-screw'19 \vh'ichf pesses through the apert'ii i'e- 7 and conflicts at its outer end with a threaded shell 29 which is secured to the lower end ofth body 1.

A screw 21 is threaded into'the bushing 18 and carries atits inner end an extensioriQE which bears 'aqziin st a eoniiii'ession' plate 23. This compression place is 's litl tibl iri the 53'ssnge 5 midis adapted to engtiefen-geinst'the resistance material il which is disposed be tween said compression plzit e and thefc'ontact strip -13] 'Ehescrevf'Ql is provided on the end opposite the extension 22, n'i'th'lu stein which projects out\ .'nr .ll beyond-the side of the body and hitsattnchctlth' reto; a thumb piece 25 by which the device is manioulzitcd.

In order to establish conneetioii between the central contact 26' of'the" plug 2 and the central contact 27 of the socket 20 a corn. tact 2G isprovided with a threaded stem 28 which extends through the bore Z-l" iihtl into the passage 4; -The 'inn'er-eiidjof 'thisste'm is-threadc'd'into abonne'tibnstrifi Qn'biir 29 the lower end of -wl iieh"terihinaite's inf the: con tnct- 9-7 which "is-{piovid edwith a" hook '30 for engagement in" the recess 10. "Irforilei" to avoid short circuitingfftheshah-2Q with the striP'Q-Q, the said shell is reee'l'ssed :i'sat 31 atthe p'oint where-the confiact sti'ip enters the mi eri An enclosing casing" to jtli'e" device coni sisting of 2 "pa'if off t e'lesco fiic "cyliiidiic'al shell memb r-1s 32 and 33'is' pi-6t icld zifi'd the member'32; is m ned at'- it's 'n'fiple'i" ehd fvitlr theshniik of the screw 2121's 86353 Tlielshe'll member 33 is armedat its lows-"ai with a 'reduc'd cyliiidrical extensioii36'- which is' adapted to enelosethe sockt gtl andlike; the shqll niember 32; 'th it'l'fipet' eiid ofthf member :3 is forr'ned w1tli':if r'' iss"which zilines with the recesses 35 tbfai'c 'e'oinrntidgi'tef theshankj'of the screw wher'i -thddet ice is assefrnblfed Each of-these membersispio vided with a linin g 3 7' -w 'icli is' presised thereinto and fornietl'of Xsnit'ablenon oon duetingor insulating material:-

In Figure 6-tl1ere is illust'rated :idevice of the same construction as that shown 'inwFig ure 2, biit instead of the finely 'dii ided filliirg' or resistance inaterial 24 irfibrous resistancematerial 38 is used; Tnthe use of sniz'h ma-' terial itdins been found desirsiblef to allow on expansion thereof and 'tor thzitreas'on'l provide spaced U sha pedplates 39 -forming* a follower. 'lhese plates. are disposed between lziyers of the resistance-materi:il :ind not only allow for expansion when the material becomes heated but also priovides a radiatingsurface to disburse the heat created by the'pessag of cnrreiit throiigh' said fibrous 'material. and further these plates operate as dec0herers,' separating themiiterial and particularly sections of material aftereach operiition oi n'hen the pressure is'releesedl In the'm odified form of the intention illustruted'in Figure 7, the de vice is illustrated as constructed for use with currents in excess of that for which the rheo stat previously described built. In this type of rheostut or controller, 2; casing 10 of ebonite oranyother siiitablenonwonductingand insul'zi ting'material isprovidetl and ono 'end wall of said cizsingearrics a contact plate a l while the opposite end wall is formed with ziiiiop'ening toreceive an internally screw threaded bushin. 42-. A fellower plate 23 formed of on suitable uniterial is provided'and carries on its inner face =1 Contact plate 4 while. the outer face of said follower" is pro'g'ideil with: swiyeled head 4.5- to 'n'hich the scrcw lti is attached. This screw46opcratcs thronglr'the bushing 42' and is" provided at its outer end with a su'itiiblethumb piece or crank {H by means of'which the Screw may" be turnedfm adjustment of the plate. T he. resistanceirnziterizil as designated by' the numeral 48 is arrangedin layersor sections between the.

arched inenibei s 4 9 which m'ny be resilient to a g'reziter or less degreew zillow for'expansion and contraction of the fibrous ninte rial LS' aiid toj rapidly radiate and disperse any} hfez'it crested; by the rise of 'teiiiij'eratnre ofthe fibrousinziterial due to the passzige of cn'iintl theietlii'oug'li! A suitable movable coiit aet iscomie'cted to the plzi'te 44 :ind when.

the inat 'erizi l 'i-eaches1 'a predet rmined point of compression"where the'fiow of current therethrough is practically at its 'rnaxii'n'um' the said movable Contact engages a stationarycqhtaet attiieh'e'd to't'he plate 11 thereby short circuitinff the resisem ee nrzit'e'rial.

' In 'Fig'ziiie 5' tliere is shownis'winding drum which may"besiibstituted lien of th'thiuhb ieceQS on which diiiniis wouri-zl' cord 50"h'iiv1'r ig its opposite e nds "extended In operation 'it will be sccnlhhtithe pl gi'j 20' threaded into anti-0.1mm" electric socket and an ordinary lump maybe secured in the socket 20 Thecentriil coiitfict of'the lamp th eje ontii c't while theeontact. y the." .r-ip' 29 will act screw 21 by rotzit-ingfthe'khob'25fthe plate. 9.3 will compress the finely divided resistance mat-erial 24 'and griltlually-creete paths of conductivity through whicli'thecurrentinzii' enter the'follo'wer 23 mul extension 22' of IOU llU

the screw 21 and thence pass through a bushing 18 and screw 19 to the socket 20. It will thus be seen that by regulating the pressure of the plate or follower 23 and the compression of the resistance material 24, the amount of current passing through the sccketmay be varied. It will be understood that when the screw 21 is advanced to a point where substantially maximum current passes through the resistance material 24, the said screw will contact with the plate 16 thereby short circuiting the resistance material as the current will enter the screw and bushing 18 through the screw 9.

Upon turning the screw 21 to retract the same it will be evident that the same will be moved away from the plate 16 and the current will again pass through the resistance material 24 and as compression becomes lessened it will be evident that paths of conductivity therethrough will be reduced until such time as little or no current will flow through the device. The operation of the device illustrated in Figures 6 and 7 is essentially the same as that previously described.

In practice it has been found that the resistance elements used in connection with the rheostat described in the foregoing are most efficient when prepared from about equal quantities of mica flakes or mineral or zinc wool and flaked carbon or graphite intimately and uniformly mixed. It has been found that two such substances, one of a conducting and the other of a non-conducting and resilient nature, having approximately the same specific gravity when thoroughly mingled will form a very efficient resistance element. Mica flakes and carbon or graphitein a finely divided state when intimately mixed also forms an excellent resistance element and has the necessary resiliency.

Other modifications may be made within the scope of the appended claims without departing from the principle or sacrificing the advantages of the invention.

\Vhat, I claim is:

1. In a compression rhcostat', a stationary contact plate. a movable contact plate, finely divided resi tance i'naterial, a rigid retaining wall confining said material between said plates, means t advance the movable plate to compress the material and create paths of conductivity thcrcthrough and means to allow for the expansion of said material when the same hecomcs hcated and to radiate the heat: created therein.

2. A device as set forth in claim 1 in which expansion and radiation are provided for by forming one of said cont-act plates of relatively thin metal.

3. A compression rheostat comprising a casing, a contact plate at one extremity of the casing a movable contact element 31".

ranged in opposed relation to the contact plate, means to move the movable contact element toward or away from the plate, layers of resilient fibrous resistance material between the contact plate and the contact element and a plurality of spaced parallel plates of a resilient conducting material arranged between the layers of resistance material to allow for expansion of the resistance material and to conduct away heat.

4. A compression rheostat comprising a casing, a stationary contact at one extremity of the casing, a movable contact in opposed relation to the stationary contact, layers of resilient compressible resistance material arranged between the contacts and pairs of spaced parallel plates of resilient conducting material arranged between the layers of resistance material whereby heat generated in the resistance material may be radiated and any expansion of the resistance material due to its heating tendencies may be compensated for.

5. In a compression rheostat, a compartment having a displaceable closure, finely divided resistance material divided in said compartment, means adapted to displace said closure for compressing said material to create paths of conductivity therethrough and means contained within said compartment to allow for the expansion of said material when the same becomes heated and to radiate the heat created therein.

6. In a compression rheostat, a container having compressible resistance material housed therein, a bodily movable follower plate, for subjecting the resistance material to compression, and means for counteracting the coherin'g effect produced by thermal and electrical forces in the rheostat in order to maintain adjustment of the resistance.

7. In a compression rheostat, a container having compressible resistance material housed therein, means for subjecting the resistance material to compression in order to adjust the resistance thereof, comprising metallic plates spaced apart but connected together, at least one of said plates contacting with said material and yieldable to compensate for the influence of thermal and electrical forces in the rheostat.

8. In a compression rheostat, a container having compressible resistance material housed therein, means for subjecting the resistance material to compression, and means "for counteracting the cohering effect produced by thermal and electrical forces in the rheostat in order to maintain the adjustmentof the resistance.

Signed in the city of New York, county and State of New York, this 25 day of April, 1919.

AARON MICAH LEVY. 

